This invention relates to extensometers for measuring axial strain and torsional deflection of a test specimen when it is subjected to load.
It is well known to be desirable to obtain both axial strain and torsional deflection readings simultaneously. Both types of strain occur even when it is sought to apply stress in only one direction. For instance, when a rod of solid material is tested for its elongation properties, the torsional deflection that accompanies axial elongation should also be measured in order to evaluate the specimen fully. Known practical techniques for determining the axial and torsional values, however, have interfered with each other and have prevented simultaneously accurate measurement. A principal object of this invention is to provide a practical device for overcoming this problem, and to enable the simultaneous measurement even when a specimen is subjected to chosen combinations of axial and torsional loading.